Stardate: 52188.7 Species 6339, as they are known to Seven of Nine, have created a virus designed to attack the Borg. Unfortunately, Voyager finds the delivery vessel, a vinculum, and Seven of Nine becomes infected. This leads to a conflict between Voyager and Species 6339, who want the vinculum back, so it can be used for its original purpose.

Recap

Incorrect Stardate
After Seven of Nine hears the Ensign Stone's log entry, she states that the Tombaugh and its crew were taken by the Borg thirteen years ago. However, the Ensign's log clearly states the Stardate as 52188.7, which is the Stardate that the episode is set in. At the end of the episode, one week later, Captain Janeway gives the Stardate as 52356.2.

Cultural References

Worried Mother: "The Best of Both Worlds"
After Seven is confined behind the forcefield in Sickbay, her personality shifts to a woman that was making a voyage to meet her son, who was stationed aboard the U.S.S. Melbourne, at Wolf 359. The Melbourne was mentioned in the Star Trek: The Next Generation "The Best of Both Worlds" story arc. It was the starship, one of many destroyed by the Borg at Wolf 359, that Commander Riker had been offered to take command of as Captain.